There’s no doubt that Hall’s plan to bring 20,000 newcomers into the four communities by 2065 is disturbing to many local residents. They like their towns just the way they are.

But despite what many of his critics would like you to believe, Hall is not the devil incarnate. Oddly enough, Hall professes to be motivated by a concern that presumably is shared by many of the Upper Valley’s save-the-planet devotees — global warming.

A hundred years from now when melting ice caps and rising sea levels force people to leave New York and Boston and head for the hills, Hall wants to have sustainable communities ready to receive them.

Maybe he’s a whack-job, but his priorities seem on target.

But after spending a couple of hours at Hall’s farmhouse in the clouds, a 450-acre spread with views of Killington, I get why he’s about as popular in Vermont as Donald Trump.

Hall, 69, is an extremely wealthy out-of-stater who is not afraid to throw his money around to get what he wants and doesn’t much care if the local citizenry shares his off-the-wall vision of the future. (He does, however, care about what state and local officials think: He’s hired one of Vermont’s top lobbying firms, Ellis Mills Public Affairs.)

“I’m used to being Mr. Bad Guy,” Hall told me, referring to the opposition he’s faced over the years in his home state of Utah, where he’s also gone on a real estate buying spree.

At last count, he’d spent $4.6 million on 15 parcels that encompass more than 1,200 acres in the Upper Valley.

And if everything goes according to his plan, he’s just begun. He’s put aside $25 million in a private foundation to buy 5,000 acres in the communities. (By comparison, the Quechee Lakes development in Hartford that was started in the late 1960s covers roughly 5,500 acres.)

The eco-friendly sustainable community Hall envisions seems straight out of Woody Allen’s Sleeper. The campus, as Hall calls it, would feature 24 four-story multi-purpose buildings with roll-up walls that would allow residents to live and work in the same space. During working hours, dining room tables, living room couches and such would be stored in cubbies under the floor.

And who would be responsible for moving the furniture around all day?

Robots, of course.

Food would be grown year-round in high-tech greenhouses — modeled after what marijuana growers are perfecting in cold-weather states such as Colorado and Washington where pot is now legal.

Hall’s opponents, who have set up a website called Stop NewVistas, aren’t impressed. “He says that he’s an environmentalist, but he doesn’t practice it,” said Michael Sacca, who represents Tunbridge on the Two Rivers-Ottauquechee Regional Commission.

Last Monday, I joined Hall in the living room of the spacious remodeled farmhouse he bought for $1.3 million at the top of Clifford Farm Road, a 2-mile dirt road in Sharon that dead ends at his driveway.

How did he settle on the Upper Valley for his grandiose social experiment?

As a kid, his Mormon family occasionally visited the birthplace of Joseph Smith, founder of the Latter Day Saint movement. His father, H. Tracy Hall, was a chemist and inventor who created the first synthetic diamonds while working for General Electric in upstate New York in 1954.

Later, his father moved the family to Utah where he helped found companies that made industrial diamonds and manufactured diamond-tipped drill bits, according to a story The New York Times wrote after his death in 2008.

David Hall, an engineer and inventor himself, has been granted more than 450 patents during his career. In 2009, he was named the top “Utah genius” for receiving the most patents in the state during the previous year, the Salt Lake Tribune reported.

Last year, Hall sold his company, Novatek, which specializes in synthetic diamond technology for the oil and gas industry, for an undisclosed amount.

Which means he has the time and money to concentrate on building his proposed community of 20,000 residents in rural Vermont where people can “live, work and play together.” (His development includes plans for 48 Olympic-size swimming pools.)

Currently, the four towns have a combined population of about 6,600 people — and no Olympic-size swimming pools that I’m aware of.

There’s nothing in local or regional growth plans to indicate that the “towns want something like this,” Sacca said. “Having a development this size in a rural area is counter to anyone’s wishes.”

Sacca, a filmmaker who moved to Vermont in the 1980s, is heading up a grassroots group of about two dozen residents that is helping lead the fight against NewVista. (They’re part of the umbrella organization, Stop NewVista, which is putting out the yard signs.)

Hall expects it will take 50 years for his proposed community to be up and running. By 2150, he envisions 1 million people living in a cluster of NewVista communities in this part of Vermont.

None of it will happen in his lifetime, he acknowledges. But his opponents are more worried about what’s happening now.

“He’s creating an artificial real estate market,” Sacca said. “People are feeling forced to sell. They don’t want to be the last one standing.”

Before his father died at age 88, Hall had a chance to lay out his NewVista plan to him. What did he think?